Exodus 38:7

38:7 He put the poles into the rings on the sides of the altar, with which to carry it. He made the altar ¹  hollow, out of boards.

Exodus 40:20

40:20 He took the testimony and put it in the ark, attached the poles to the ark, and then put the atonement lid on the ark.

[38:7]  ¹ tn Heb “it”; the referent (the altar) has been specified in the translation for clarity.